Classic 40-Year-Old Marshmallow Test Gets Revisited With New Study

October 11, 2012

Caption: Evelyn Rose, 4, of Brighton, N.Y. participates in a reenactment of the marshmallow experiment. The study found that children's decisions to delay gratification is influenced as much by the environment as by their innate capacity for self-control. The study was conducted at the University of Rochester Baby Lab. Credit: J. Adam Fenster / University of Rochester

Breakthrough research in the 1960s that used marshmallows to assess a child´s ability to delay gratification has been revisited with a fresh, new updated study by researchers from the University of Rochester.

In the landmark study from the 60s and 70s, researchers used either marshmallows or cookies to study the effects of child self-control. In those studies, if a child could hold off on the temptation to eat the yummy snack, he or she would be rewarded with more treats later.

In the study, published in the October 11 issue of the journal Cognition, researchers from Rochester University demonstrate that being able to delay gratification is influenced as much by the environment as by instinctive ability. Children participating in the study who experienced reliable interactions immediately before the test began waited on average four times longer (12 minutes versus 3 minutes) than youngsters who were in unreliable situations.

This study follows another published last August in the issue of the Proceedings of the National Academy of Sciences (PNAS), in which study researchers from Cornell University used a group of the same children, now adults, from the earlier experiments from the 60s and 70s, in an updated experiment.

In that study, reported on by redOrbit.com in September 2011, the researchers found that those who were better at delaying gratification as children, showed similar behaviors as adults; and for those who wanted their treat right away as a child, were also more likely to seek instant gratification as an adult. Brain imaging also showed key differences between both groups in two distinct areas: the prefrontal cortex and the ventral striatum.

In the study, participants looked at a screen displaying a series of faces and were asked to signal only when a face of one gender was shown. Called a “cool” test, this experiment revealed no significant differences between the two groups. In the second experiment–the “hot” test– participants were shown faces displaying emotional cues, such as happy, sad and frightened. In this test, researchers found more varied results revealing that aptitude for delayed gratification was consistent from childhood to adulthood.

“In this test, a happy face took the place of the marshmallow. The positive social cue interfered with the low delayer´s ability to suppress his or her actions,” said researchers.

The second test was repeated while the participant´s brain was scanned using functional magnetic resonance imaging (fMRI). The results showed that the brain´s prefrontal cortex was more active for high delayers and the ventral striatum – an area linked to addictions – was more active in low delayers.

“This is the first time we have located the specific brain areas related to delayed gratification. This could have major implications in the treatment of obesity and addictions,” said, at the time, lead author of the study, Dr. B.J. Casey, director of the Sackler Institute for Developmental Psychobiology at Weill Cornell Medical College.

Though following the Cornell study, as well as the past experiments, the new Rochester study looked more closely at why some preschoolers were able to resist the marshmallow while others succumbed to sniffing, licking, nibbling and eventually devouring the little, white, sugary, cylindrical treat.

In their study, the researchers assigned 28 preschoolers between the ages of 3 and 5 to two contrasting environments: reliable and unreliable. The study results were so significant that a larger sample group was not required to ensure statistical accuracy.

Both groups of children were given a create-your-own-cup kit and were asked to decorate some blank paper that would be placed in the cup.

In the unreliable environment group, children were provided a container of used crayons and told that if they could wait, a person would return with a better set of supplies for their project. After about 2.5 minutes, a person returned with an apology that a mistake was made and there would be no better supplies handed out, but asked the children to still create the art project with the original supplies offered.

Next, a quarter-inch sticker was placed on the table and the child was told that if he or she could wait, somebody would return with a large selection of better stickers to use. After the same 2.5-minute wait, the person would return empty handed with another apology.

In the reliable environment group, the same set-up was used, but the researcher always returned with promised materials.

After using these experiments as a base-line, the researchers began the marshmallow test, telling the children they could have “one marshmallow right now. Or–if you can wait for me to get more marshmallows from the other room–you can have two marshmallows to eat instead.”

The researcher removed the art supplies and placed the single marshmallow in a small desert dish on the table in front of the child. Researchers and parents watched a video feed from another room until either fifteen minutes had passed or a marshmallow was eaten, whichever came first. In this phase of the experiment, all children received three additional marshmallows in the end.

“Watching their strategies for waiting was quite entertaining,” said Holly Palmeri, coauthor and coordinator of the Rochester Baby Lab at the University of Rochester.

It was entertaining watching the kids dance in their seats, singing, taking pretend naps; several kids took bites from the bottom of the marshmallow than placed it back in the cup so it looked untouched. Interestingly, a few kids nibbled from both ends, and after realizing they could no longer hide the evidence, devoured the treat, Palmeri explained.

“We had one little boy who grabbed the marshmallow immediately and we thought he was going to eat it,” said Celeste Kidd, a doctoral candidate in brain and cognitive sciences at the University of Rochester and lead author of the study.

Instead he sat on it, Kidd joked. “Instead of covering his eyes, he covered the marshmallow.”

Analysis of the study revealed that children who were in the unreliable environment group waited an average of three minutes and two seconds before succumbing to the gooey goodness of the marshmallow treat. Meanwhile, the children in the reliable environment group held out for an average of 12 minutes and two seconds.

Only one child in the unreliable group held out the full 15 minutes, compared to nine children in the reliable group, noted the researchers.

“Our results definitely temper the popular perception that marshmallow-like tasks are very powerful diagnostics for self-control capacity,” said Kidd.

“Being able to delay gratification–in this case to wait 15 difficult minutes to earn a second marshmallow–not only reflects a child’s capacity for self-control, it also reflects their belief about the practicality of waiting,” Kidd explained. “Delaying gratification is only the rational choice if the child believes a second marshmallow is likely to be delivered after a reasonably short delay.”

Study coauthor, Richard Aslin, the William R. Kenan Professor of brain and cognitive sciences at Rochester, said the findings provide an important reminder about the complexity of human behavior.

“This study is an example of both nature and nurture playing a role“¦We know that to some extent, temperament is clearly inherited, because infants differ in their behaviors from birth. But this experiment provides robust evidence that young children’s action are also based on rational decisions about their environment,” explained Aslin.

Aslin said he was shocked the effect was so large. “I thought that we might get a difference of maybe a minute or so“¦ You don’t see effects like this very often.”

In past research, children´s wait times averaged between 6.08 and 5.71 minutes, the authors reported. By manipulating the environment, wait times doubled in the reliable group and were halved in the unreliable environment.

The authors conclude that manipulating the environment provides strong evidence that children’s wait times reflect rational decision making about the probability of reward. The results are consistent with other research showing that children are sensitive to uncertainty in future rewards.

Aslin noted, however, that parents should not be worried by watching their kids gobble up their treat because of the unreliability they were subjected to in the study.

“Children do monitor the behavior of parents and adults, but it is unlikely that they are keeping detailed records of every single action“¦It’s the overall sense of a parent’s reliability or unreliability that’s going to get through, not every single action,” Aslin explained.

“Don’t do the marshmallow test on your kitchen table and conclude something about your child. It especially would not work with a parent, because your child has all sorts of strong expectations about what a person who loves them very much is likely to do,” added Kidd.

These studies build on the previous gratification research that first started at Stanford University in the 1960s. Walter Mischel and other researchers showed that individual differences in the ability to delay gratification on a simple task correlated strongly with success later in life. Longer wait times as a child were linked years later to higher SAT scores, less instances of substance abuse, and better social skills.

The correlations found in the landmark marshmallow studies have been cited as evidence that qualities like self-control and emotional intelligence may be more important in life than more traditional measures of intelligence, such as IQ testing.